Surprisingly strong "electrical" smell around the vent ports.
Blown TOP244YN , 20 ohms across rectified mains cap.
Considering crack to its encapsulation is just observable, on one side
only and then under x30. Distorted top to the sillypad (TM) , what may
be a puncture hole at the non-rounded, but then not sharp, rear upper edge.
Hang on a bit , although the tab holding bolt has an insulating washer,
the heatsink is isolated, anti-EMI ?. So if it did puncture , why
leading to failure?
Any known problems with these presumably fairly generic SMPS sub-units,
all else checks out (cold) ok. Mica will be going back in there.